Semiconductor wafer assembly and machining apparatus having chuck tables for holding the same

ABSTRACT

A semiconductor wafer assembly is constituted such that the back surface of a tape is stuck to the surface of a frame and a semiconductor wafer is stuck to the surface of the tape. A machining apparatus has chuck tables for supporting the semiconductor wafer assembly, and each of the chuck tables has a semiconductor wafer placing surface for supporting the back surface of the tape to which the semiconductor wafer is stuck and an annular frame placing surface for supporting the back surface of the frame, formed, in the outer peripheral side of the semiconductor wafer mounting surface, at a position below the semiconductor wafer placing surface with a level difference therebetween.

FIELD OF THE INVENTION

[0001] The present invention relates to a semiconductor wafer assemblyto be held on a chuck table when a semiconductor wafer is to bemachined, and to a machining apparatus having chuck tables for holdingthe same.

DESCRIPTION OF THE PRIOR ART

[0002] As known to people of ordinary skill in the art, in asemiconductor device production process, a substantially disk-likesemiconductor wafer is divided into individual pellets to formsemiconductor chips. To improve the heat radiation properties of thesemiconductor chip, the semiconductor chip is desirably made as thin aspossible. Also to enable the downsizing of a portable telephone, smartcard and personal computer in which a large number of semiconductorchips are used, the semiconductor chip is desirably made as thin aspossible. To this end, prior to the semiconductor wafer is divided intopellets, the back surface of the semiconductor wafer is ground tomachine it to have a predetermined thickness. In a grinding machine forgrinding the back surface of the semiconductor wafer, the semiconductorwafer as a workpiece is suction-held on a chuck table, and the backsurface of the semiconductor wafer whose top surface is suction-held onthe chuck table is ground by a grinding means.

[0003] When the semiconductor wafer is thus ground up to a thickness of100 μm or less, for example, the rigidity of the semiconductor waferlowers and consequently, flexure occurs in the entire semiconductorwafer, thereby making it difficult to transport and store in a cassettethe semiconductor wafer. Further, in a so-called “pre-dicing” productionmethod that dicing grooves having a predetermined depth from the surfaceare in advance formed by a dicing machine and then, the back surface ofthe semiconductor wafer is finished to have a thickness of about 50 μmby grinding it to divide the semiconductor wafer into chips, the groundsemiconductor wafer does not fall apart into chips owing to the functionof a protective tape stuck to the surface side of the semiconductorwafer but it does not have rigidity at all as a semiconductor wafer,thereby making it extremely difficult to transport the semiconductorwafer after grinding.

[0004] To make it easy to transport and store in a cassette thesemiconductor wafer after grinding, it is conceivable that asemiconductor wafer assembly is constructed by mounting a semiconductorwafer on a frame by a tape like a case where dicing is carried out, forexample, and the semiconductor wafer assembly in this state is groundand transported. However, the semiconductor wafer assembly which is usedfor dicing machining is constituted such that a tape is stuck to theback surface of an annular frame and a semiconductor wafer is stuck tothe top surface of the tape so that the semiconductor wafer and theframe are arranged on the same plane. Therefore, there is a problem thatas the frame is existent on the side of the semiconductor wafer, agrinding wheel interferes with the frame at the time when thesemiconductor wafer is ground.

SUMMARY OF THE INVENTION

[0005] It is an object of the present invention to provide asemiconductor wafer assembly which makes it easy to transport asemiconductor wafer after machining and prevents a member other than thesemiconductor wafer from interfering with a machining tool duringmachining, and a machining apparatus having chuck tables for holding thesemiconductor wafer assembly.

[0006] To attain the above object, according to the present invention,there is provided a semiconductor wafer assembly consisting of anannular frame, a tape mounted to the frame and a semiconductor waferstuck to the tape, wherein

[0007] the back surface of the tape is stuck to the surface of theframe, and the semiconductor wafer is stuck to the surface of the tape.

[0008] An adhesion layer is formed in at least an area where thesemiconductor wafer is arranged, of the surface of the tape and anadhesion layer is also formed in an area which sticks to the surface ofthe frame, of the back surface of the tape. A cutout corresponding to acutout showing the crystal orientation of the semiconductor wafer isformed in an outer circumferential portion of the frame and the bothcutouts are aligned with each other.

[0009] According to the present invention, there is provided asemiconductor wafer assembly consisting of an annular frame, a tapemounted to the frame, a semiconductor wafer stuck to the surface of thetape and a fixing ring for fixing the periphery portion of the tape tothe frame, wherein

[0010] the annular frame consists of an annular frame portion and anannular mounting portion that projects upward from the inner peripheralportion of the frame portion, and

[0011] the tape is placed to the surface of the mounting portion, thefixing ring is fitted onto the outer circumferential portion of themounting portion to sandwich the periphery portion of the tape betweenthe outer peripheral surface of the mounting portion and the innerperipheral surface of the fixing ring.

[0012] A cutout corresponding to a cutout showing the crystalorientation of the semiconductor wafer is formed in an outercircumferential portion of the frame portion of the frame and the bothcutouts are aligned with each other.

[0013] According to the present invention, there is provided a machiningapparatus comprising chuck tables having a placing surface forsuction-holding a semiconductor wafer assembly and a machining means formachining the semiconductor wafer of the semiconductor wafer assemblysuction-held on the chuck tables, wherein

[0014] the semiconductor wafer assembly consists of an annular frame, atape mounted to the frame and a semiconductor wafer stuck to the surfaceof the tape, and

[0015] each of the chuck tables has a semiconductor wafer placingsurface for supporting the back surface of the tape to which thesemiconductor wafer is stuck and an annular frame placing surface forsupporting the back surface of the frame, formed, on the outerperipheral side of the semiconductor wafer placing surface, at aposition below the semiconductor wafer placing surface with a leveldifference therebetween.

[0016] The level difference between the semiconductor wafer placingsurface and the frame placing surface is desirably equivalent to thethickness of the frame. The suction ports of communication pathsconnected to a suction source are desirably formed in the frame placingsurface. The above machining means is a grinding means for grinding thesemiconductor wafer of the semiconductor wafer assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a perspective view of a semiconductor wafer assemblyconstructed according to an embodiment of the present invention;

[0018]FIG. 2 is a sectional view cut on A-A of FIG. 1;

[0019]FIG. 3 is a perspective view, in a disassembled way, of theconstituent members of the semiconductor wafer assembly shown in FIG. 1;

[0020]FIG. 4 is a perspective view of a semiconductor wafer assemblyconstructed according to another embodiment of the present invention;

[0021]FIG. 5 is a sectional view cut on B-B of FIG. 4;

[0022]FIG. 6 is a perspective view, in a disassembled way, of theconstituent members of the semiconductor wafer assembly shown in FIG. 4;

[0023]FIG. 7 is a perspective view of a surface grinding machine as amachining apparatus constructed by the present invention;

[0024]FIG. 8 is a perspective view of an embodiment of a chuck tablemounted in the surface grinding machine shown in FIG. 7;

[0025]FIG. 9 is a sectional view showing a state where the semiconductorwafer assembly shown in FIGS. 1 to 3 is held on the chuck table shown inFIG. 8; and

[0026]FIG. 10 is a sectional view of another embodiment of a chuck tablemounted in the surface grinding machine shown in FIG. 7 and shows astate where it holds the semiconductor wafer assembly shown in FIGS. 4to 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] A semiconductor wafer assembly and a grinding machine constructedaccording to preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawingshereinafter.

[0028]FIG. 1 is a perspective view of a semiconductor wafer assemblyconstructed according to a preferred embodiment of the presentinvention, FIG. 2 is a sectional view cut on A-A of FIG. 1, and FIG. 3is a perspective view, in a disassembled way, of the constituent membersof the semiconductor wafer assembly shown in FIG. 1. The semiconductorwafer assembly 2 of the illustrated embodiment consists of an annularframe 21, a tape 22 mounted to the frame 21 and a semiconductor wafer 23stuck to the tape 22. The annular frame 21 is formed from a thin plateas thick as about 1 mm, that is made from stainless steel or the like,for example. The tape 22 is formed in a circular form from anappropriate resin film, an adhesion layer 221 is formed on the surfaceside (upper side in FIG. 2) of the tape 22 and an adhesion layer 222 isformed on the back side (lower side in FIG. 2) of the periphery portionof the tape 22. The adhesion layer 222 on the back side (lower side inFIG. 2) of the periphery portion of the thus constructed tape 22 isstuck to the surface (upper side in FIG. 2) of the above frame 21. Thesemiconductor wafer assembly 2 is constructed by sticking thesemiconductor wafer 23 to the adhesion layer 221 on the surface of thetape 22 of which the back surface of the peripheral portion is stuck tothe surface of the annular frame 21. At this point, the adhesion layerto be formed on the surface of the tape 22 may be formed in at least anarea where the semiconductor wafer 23 is arranged. The adhesion layer222 formed on the back surface of the periphery portion of the tape 22is not always necessary. In this case, an adhesion layer is formed onthe surface of the frame 21 to stick the back surface of the peripheryportion of the tape 22 thereto. A cutout 21 a corresponding to a cutout23 a showing a crystal orientation of the semiconductor wafer 23 isformed at a predetermined position of an outer circumferential portionof the frame 21. Therefore, when the semiconductor wafer 23 is to bemounted on the surface of the tape 22 stuck to the frame 21, it ismounted at a position where the cutout 23 a formed in the semiconductorwafer 23 is aligned with the cutout 21 a formed in the frame 21, therebymaking it possible to confirm the crystal orientation of thesemiconductor wafer 23 in the transportation.

[0029] A semiconductor wafer assembly according to another embodimentwill be described with reference to FIGS. 4 to 6.

[0030] The semiconductor wafer assembly 3 of this embodiment consists ofan annular frame 31, a tape 32 mounted to the frame 31, a semiconductorwafer 33 stuck to the tape 32 and an annular fixing ring 34 for fixingthe tape 32 to the frame 31. The annular frame 31 consists of an annularframe portion 311 and an annular mounting portion 312 projecting upwardfrom the inner peripheral portion of the frame portion 311 and is madefrom a metal material such as stainless steel. The tape 32 is formed ina circular form from an appropriate resin film, and an adhesion layer321 is formed on the surface (upper side in FIG. 5) of the tape 32. Theouter diameter of the tape 32 is made larger than the outer diameter ofthe annular mounting portion 312 constituting the above annular frame 31by a size corresponding to the height of the mounting portion 312. Thesemiconductor wafer 33 is stuck to the adhesion layer 321 on the surfaceof the tape 32. The above annular fixing ring 34 has an inner diameterslightly larger than the outer diameter of the annular mounting portion312 constituting the above annular frame 31, and is made from a metalmaterial such as stainless steel, for example. The tape 32 is placed onthe surface side (upper side) of the mounting potion 312 constitutingthe above annular frame 31, and the fixing ring 34 is fitted onto theouter circumferential portion of the mounting portion 312 to sandwichthe periphery portion of the tape 32 between the outer peripheralsurface of the mounting portion 312 and the inner peripheral surface ofthe fixing ring 34, thereby making it possible to fix the tape 32 to theframe 31. Since the tape 32 is sandwiched between the mounting portion312 of the frame 31 and the fixing ring 34, an adhesion layer does notneed to be formed on the back surface of the tape 32. A cutout 311 acorresponding to a cutout 33 a showing the crystal orientation of thesemiconductor wafer 33 is formed at a predetermined position of an outercircumferential portion of the frame portion 311 constituting theannular frame 31. Therefore, the semiconductor wafer 33 is mounted at aposition where the cutout 33 a formed in the semiconductor wafer 33 isaligned with the cutout 311 a, thereby making it possible to confirm thecrystal orientation of the semiconductor wafer 33 in the transportation.

[0031] A description is subsequently given of a grinding machine forgrinding the semiconductor wafer 23 by holding the semiconductor waferassembly 2 as shown in FIG. 1 with reference to FIG. 7 and FIG. 8.

[0032] The grinding machine of the illustrated embodiment comprises asubstantially rectangular parallelepiped housing 4. A static supportplate 6 is provided upright at a right upper end of the housing 4 inFIG. 7. Two pairs of guide rails 7,7 and 8,8 extending in a verticaldirection are provided on the inside surface of the static support plate6. A rough-grinding unit 10 as a rough-grinding means is mounted to onepair of guide rails 7,7 in such a manner that it can move in an up anddown direction, and a finish-grinding unit 12 as a finish-grinding meansis mounted to the other pair of guide rails 8,8 in such a manner that itcan move in an up and down direction.

[0033] The rough-grinding unit 10 comprises a unit housing 101, agrinding wheel 102 rotatably attached to the lower end of the unithousing 101, a rotary drive unit 103, mounted to the upper end of theunit housing 101, for rotating the grinding wheel 102 in a directionindicated by an arrow, and a movable base 104 mounting the unit housing101. To-be-guide rails 105,105 are provided on the movable base 104 andmovably fitted to guide rails 7,7 provided on the above static supportplate 6 so that the rough-grinding unit 10 is supported movably in an upand down direction. The rough-grinding unit 10 of the illustratedembodiment comprises a feeding unit 11 for moving the above movable base104 along the guide rails 7,7 to adjust the cutting depth of thegrinding wheel 102. The feeding unit 11 comprises a male screw rod 111which is rotatably provided in an up and down direction in parallel tothe guide rails 7,7 and supported to the above static support plate 6, apulse motor 112 for rotary-driving the male screw rod 111 and an femalescrew block (not shown) that is mounted on the movable base 104 andmeshed with the male screw rod 111. The male screw rod 111 is driven ina forward direction or reverse direction by the pulse motor 112 to movethe rough-grinding unit 10 in an up and down direction.

[0034] The above finish-grinding unit 12 has the same constitution asthat of the rough-grinding unit 10. That is, it comprises a unit housing121, a grinding wheel 122 rotatably attached to the lower end of theunit housing 121, a rotary drive unit 123, attached to the upper end ofthe unit housing 121, for rotating the grinding wheel 122 in a directionindicated by an arrow, and a movable base 124 mounting the unit housing121. To-be-guide rails 125,125 are provided on the movable base 124, andmovably fitted to guide rails 8,8 provided on the above static supportplate 6 so that the finish-grinding unit 12 is supported movably in anup and down direction. The finish-grinding unit 12 of the illustratedembodiment comprises a feeding unit 13 for moving the above movable base124 along the guide rails 8,8 to adjust the cutting depth of thegrinding wheel 122. The feeding unit 13 has substantially the sameconstitution as the above feeding means 11. That is, the feeding unit 13comprises a male screw rod 131 which is rotatably provided in an up anddown direction in parallel to the guide rails 8, 8 and supported to theabove static support plate 6, a pulse motor 132 for rotary-driving themale screw rod 131 and a female screw block (not shown) mounted on themovable base 124 and fitted to the male screw rod 131. The male screwrod 131 is driven in a forward direction or reverse direction by thepulse motor 132 to move the finish-grinding unit 12 in an up and downdirection.

[0035] The grinding machine of the illustrated embodiment has a turntable 15 which is disposed substantially flush with the top surface ofthe housing 4 on the front side of the above static support plate 6.This turn table 15 is formed like a disk having a relatively largediameter and suitably rotated in a direction indicated by an arrow 15 aby a rotary drive unit that is not shown. In the illustrated embodiment,three chuck tables 5 are arranged each other at a phase angle of 120°rotatably on the horizontal plane on the turn table 15. The chuck tables5 are suitable for holding the semiconductor wafer assembly 2 shown inFIGS. 1 to 3 and will be descried in detail with reference to FIG. 8 andFIG. 9. The chuck table 5 shown in FIG. 8 and FIG. 9 consists of adisk-like base 51 and a disk-like suction-holding chuck 52. The base 51is made from a metal material such as stainless steel, and a rotaryshaft portion 511 projects from the center portion of the under surfacethereof and is rotatably supported onto the turn table 15 by a bearingthat is not shown. Since the rotary shaft portion 511 is connected to arotary drive unit that is not shown, the chuck table 5 is caused torotate in a direction indicated by an arrow in FIG. 7 when the rotarydrive unit is activated.

[0036] A circular depressed portion 512 whose top portion is open isformed in the top surface of the base 51 and is connected to acommunication path 513 provided in the rotary shaft portion 511. Thecommunication path 513 is connected to a suction source that is notshown. The above suction-holding chuck 52 is formed of a porous ceramicdisk and is fitted in the depressed portion 512 formed in the above base51. Thus, the top surface of the suction-holding chuck 52 fitted in thedepressed portion 512 of the base 51 serves as a semiconductor waferplacing surface 521 for supporting the back surface of the tape 22 towhich the semiconductor wafer 23 of the above semiconductor waferassembly 2 has been stuck, as will be described hereinafter. On theouter peripheral side of depressed portion 512 in the top surface of thebase 51, an annular frame placing surface 514 for supporting the backsurface of the frame 21 of the semiconductor wafer assembly 2 is formedat a position below the semiconductor wafer placing surface (topsurface) of the suction-holding chuck 52 with a level difference 515therebetween. The level difference 515 of this annular frame placingsurface 514 is equivalent to the thickness of the frame 21. The suctionports 517 of a plurality of communication paths 516 connected to thedepressed portion 512 are formed in the annular frame placing surface514.

[0037] On the chuck table 5 constituted as described above is placed thesemiconductor wafer assembly 2 as shown in FIG. 9. That is, the backsurface of the tape 22 to which the semiconductor wafer 23 is stuck isplaced on the semiconductor wafer placing surface 521 which is the topsurface of the suction-holding chuck 52, and the back surface of theframe 21 is placed on the annular frame placing surface 514. Byconnecting the communication path 513 to the suction source (not shown),the semiconductor wafer assembly 2 can be suction-held on thesuction-holding chuck 5. Therefore, the frame 21 is located at aposition lower than the semiconductor wafer 23 by the above leveldifference 515. Consequently, while the semiconductor wafer 23 isground, the grinding wheels 102 and 122 do not interfere with the frame21. The three chuck tables 5 arranged on the turn table 15 constitutedas described above are moved to a workpiece carrying-in/carrying-outarea A, rough-grinding area B, finish-grinding area C and workpiececarrying-in/carrying-out A in this order by properly turning the turntable 15.

[0038] The illustrated grinding machine comprises a first cassette 41,arranged on one side relative to the workpiece carrying-in/carrying-outarea A, for storing the semiconductor wafer assembly 2 which is aworkpiece before grinding, a second cassette 42, arranged on the otherside relative to the workpiece carrying-in/carrying-out area A, forstoring the semiconductor wafer assembly 2 after grinding, a workpieceplacing unit 43 provided between the first cassette 41 and the workpiececarrying-in/carrying-out area A, a cleaning means 44 provided betweenthe workpiece carrying-in/carrying-out area A and the second cassette42, a workpiece delivering means 45 for delivering the semiconductorwafer assembly 2 stored in the first cassette 41 to the workpieceplacing unit 43 and delivering the semiconductor wafer assembly 2cleaned by the cleaning means 44 to the second cassette 42, a workpiececarrying-in means 46 for carrying the semiconductor wafer assembly 2placed on the workpiece placing unit 43 to the top of the chuck table 4positioned in the workpiece carrying-in/carrying-out area A, and aworkpiece carrying-out means 47 for carrying the semiconductor waferassembly 2 after grinding placed on the chuck table 5 positioned in theworkpiece carrying-in/carrying-out area A to the cleaning means 44.

[0039] The semiconductor wafer assembly and the grinding machine in theillustrated embodiment are constituted as described above, and theirfunctions will be described hereinafter.

[0040] The semiconductor wafer assembly 2 before grinding stored in thefirst cassette 41 is carried by the up and down movement and forward andreverse movement of the workpiece delivering means 45, mounted on theworkpiece placing unit 43 and centered by the radial movement toward thecenter of six pins 431. The semiconductor wafer assembly 2 which hasbeen mounted on the workpiece placing unit 43 and has centered is placedon the chuck table 5 positioned in the workpiececarrying-in/carrying-out area A by the turning movement of the workpiececarrying-in means 46. When the communication path 513 formed in the base51 of the chuck table 5 is connected to the suction source (not shown),the back surface of the tape 22 to which the semiconductor wafer 23 isstuck, of the semiconductor wafer assembly 2 mounted on the chuck table5, is sucked to the semiconductor wafer placing surface 521 of thesuction-holding chuck 52 and the back surface of the frame 21 issuction-held on the annular frame placing surface 514. When thesemiconductor wafer assembly 2 is suction-held on the chuck table 5, theturn table 15 is turned at 120° in a direction indicated by the arrow 15a by the rotary drive unit (not shown) to position the chuck table 5 onwhich the semiconductor wafer assembly 2 has been placed in therough-grinding area B.

[0041] When the chuck table 5 on which the semiconductor wafer has beenplaced is positioned in the rough-grinding area B, it is turned in adirection indicated by an arrow by the rotary drive unit (not shown),and the grinding wheel 102 of the rough-grinding unit 10 is, while beingrotated in a direction indicated by an arrow, lowered a predeterminedamount by the feeding unit 11 so that the semiconductor wafer 23 of thesemiconductor wafer assembly 2 on the chuck table 5 is roughly ground.At this point, since the frame 21 of the semiconductor wafer assembly 2held on the chuck table 5 is located at a position lower than thesemiconductor wafer 23 by the above level difference 515 as describedabove, the frame 21 does not interfere with the grinding wheel 102 atthe time when the semiconductor wafer 23 is ground by the grinding wheel102. Further, since the semiconductor wafer placing surface 521 and theannular frame placing surface 514 of the chuck table 5 are covered withthe frame 21 and the tape 22, contaminants generated by grinding do notcontaminate the placing surfaces, thereby making it possible to maintainthe function of the chuck table with high accuracy. While this grindingwork is thus carried out, the semiconductor wafer assembly 2 beforegrinding is mounted on the next chuck table 5 positioned in theworkpiece carrying-in/carrying-out area A, as described above. The chucktable 5 on which the roughly ground semiconductor wafer assembly 2 hasbeen placed is then positioned in the finish-grinding area C by turningthe turn table 15 at 120° in a direction indicated by the arrow 15 a. Atthis point, the next chuck table 5 on which the semiconductor waferassembly 2 has been placed in the workpiece carrying-in/carrying-outarea A is positioned in the rough-grinding area B, and the chuck table 5after the next is positioned in the workpiece carrying-in/carrying-outarea A.

[0042] The semiconductor wafer 23 of the semiconductor wafer assembly 2before rough-grinding placed on the chuck table 5 positioned in therough-grinding area B is thus roughly ground by the rough-grinding unit10 and the semiconductor wafer 23 of the semiconductor wafer assembly 2placed on the chuck table 5 positioned in the finish-grinding area C androughly ground is finish-ground by the finish-grinding unit 12. Duringthis finish-grinding, too, the frame 21 of the semiconductor waferassembly 2 held on the chuck table 2 is located at a position lower thanthe semiconductor wafer 23 by the level difference 515. Therefore, whilethe semiconductor wafer 23 is ground by the grinding wheel 122, theframe 21 does not interfere with the grinding wheel 122. The chuck table5 on which the finish-ground semiconductor wafer assembly 2 has beenplaced is then positioned in the workpiece carrying-in/carrying-out areaA by turning the turn table 15 at 120° in a direction indicated by thearrow 15 a. The chuck table 5 on which the semiconductor wafer assembly2 roughly ground in the rough-grinding area B is placed is moved to thefinish-grinding area C and the chuck table 5 on which the semiconductorwafer assembly 2 before grinding in the workpiececarrying-in/carrying-out area A is placed is moved to the rough-grindingarea B, respectively.

[0043] The chuck table 5 that has returned to the workpiececarrying-in/carrying-out area A via the rough-grinding area B and thefinish-grinding area C releases here the suction-holding of the finishground semiconductor wafer assembly 2. That is, communication betweenthe communication path 513 formed in the base 51 of the chuck table 5and the suction source (not shown) is cut off. The finish-groundsemiconductor wafer assembly 2 on the chuck table 5 positioned in theworkpiece carrying-in/carrying-out area A is carried to the cleaningmeans 44 by the workpiece carrying-out means 47. The semiconductor waferassembly 2 carried to the cleaning means 44 is cleaned and then storedat a predetermined position of the second cassette 42 by the workpiecedelivering means 45.

[0044] A chuck table 5 a suitable for holding the semiconductor waferassembly 3 shown in FIGS. 4 to 6 will be described with reference toFIG. 10.

[0045] The chuck table 5 a shown in FIG. 10 consists of a disk-like base51 a and a disk-like suction-holding chuck 52 a, like the chuck table 5shown in FIGS. 8 and 9. The base 51 a is made from a metal material suchas stainless steel, and a rotary shaft portion 511 a projects from thecenter portion of the under surface thereof and is rotatably supportedto the above turn table 15 of the grinding machine shown in FIG. 7 by abearing that is not shown.

[0046] A circular depressed portion 512 a whose top portion is open isformed in the top surface of the base 51 a and is connected to acommunication path 513 a provided in the rotary shaft portion 511 a andconnected to the suction source that is not shown. The suction-holdingchuck 52 a is formed of a porous ceramic disk and is fitted in thedepressed portion 512 a formed in the above base 51 a. Thus, the topsurface of the suction-holding chuck 52 a fitted in the depressedportion 512 a of the base 51 a serves as a semiconductor wafer placingsurface 521 a for supporting the back surface of the tape 32 to whichthe semiconductor wafer 33 of the above semiconductor wafer assembly 3is stuck, as will be described hereinafter. In the outer peripheral sideof the depressed portion 512 a in the top surface of the base 51 a, anannular frame placing surface 514 a for supporting the back surface ofthe frame portion 311 constituting the frame 31 of the semiconductorwafer assembly 3 is formed at a position below the semiconductor waferplacing surface (top surface) of the suction-holding chuck 52 a with alevel difference 515 a therebetween. The level difference 515 a of thisannular frame placing surface 514 a is equivalent to the total of thethickness of the frame portion 311 and the thickness of the mountingportion 312 constituting the frame 31. The suction ports 517 a of aplurality of communication paths 516 a connected to the abovecommunication path 513 a are formed in the annular frame placing surface514 a.

[0047] On the chuck table 5 a constituted as described above is placedthe semiconductor wafer assembly 3 as shown in FIG. 10. That is, theback surface of the tape 32 to which the semiconductor wafer 33 is stuckis placed on the semiconductor wafer placing surface 521 a which is thetop surface of the suction-holding chuck 52 a, and the back surface ofthe frame portion 311 constituting the above frame 31 is placed on theannular frame placing surface 514 a. By connecting the communicationpath 513 a to the suction source (not shown), the semiconductor waferassembly 3 can be suction-held on the suction-holding chuck 5 a.Therefore, the frame 31 is located at a position lower than thesemiconductor wafer 33 by the level difference 515 a. Consequently,while the semiconductor wafer 23 is ground, the grinding wheels 102 and122 of the grinding machine shown in FIG. 7 do not interfere with theframe 31. Since the semiconductor wafer placing surface 521 a and theannular frame placing surface 514 a of the chuck table 5 a are coveredwith the frame 31 and the tape 32, contaminants generated by grinding donot contaminate the mounting surfaces, thereby making it possible tomaintain the function of the chuck table with high accuracy.

[0048] Since the semiconductor wafer assembly and the machiningapparatus according to the present invention are constituted asdescribed above, the following function and effect are obtained.

[0049] That is, according to the present invention, since the backsurface of the tape of the semiconductor wafer assembly is stuck to thesurface of the frame and the semiconductor wafer is stuck to the surfaceof the above tape, the semiconductor wafer and the frame are located onopposite sides of the tape, whereby while the semiconductor wafer isground, the machining tools do not interfere with the frame, therebymaking it possible to machine the semiconductor wafer smoothly. Further,as the machined semiconductor wafer is united with the frame via thetape, it is not bent by the rigidity of the frame and can be deliveredsmoothly and stored in the cassette, even if it has been made thin ordivided.

[0050] According to the present invention, the semiconductor waferassembly consists of an annular frame, a tape mounted to the frame, asemiconductor wafer stuck to the surface of the tape and a fixing ringfor fixing the periphery portion of the tape to the frame, the tape isplaced to the surface of the mounting portion constituting the annularframe, the fixing ring is fitted onto the outer circumferential portionof the mounting portion to sandwich the outer peripheral portion of thetape between the outer peripheral surface of the mounting portion andthe inner peripheral surface of the fixing ring. Therefore, the tape canbe mounted to the frame without forming an adhesion layer on the backsurface of the tape.

[0051] The machining apparatus according to the present invention isconstituted such that the chuck table for holding the semiconductorwafer assembly has a semiconductor wafer placing surface for supportingthe back surface of the tape to which the semiconductor wafer is stuckand an annular frame placing surface for supporting the back surface ofthe frame, which is formed, in the outer peripheral side of thesemiconductor wafer placing surface, at a position below thesemiconductor wafer placing surface with a level differencetherebetween. Therefore, the frame is located at a position where themachining tool does not interfere with the frame during the machining ofthe semiconductor wafer, thereby making it possible to machine thesemiconductor wafer smoothly. Further, as the semiconductor waferplacing surface and the annular frame placing surface of the chuck tableare covered with the frame and the tape, contaminants generated bygrinding do not contaminate the placing surfaces, thereby making itpossible to maintain the function of the chuck table with high accuracy.

What is claimed is:
 1. A semiconductor wafer assembly consisting of anannular frame, a tape mounted to the frame and a semiconductor waferstuck to the tape, wherein the back surface of the tape is stuck to thesurface of the frame and the semiconductor wafer is stuck to the surfaceof the tape.
 2. The semiconductor wafer assembly of claim 1, wherein anadhesion layer is formed in at least an area where the semiconductorwafer is arranged, of the surface of the tape and an adhesion layer isalso formed in an area in contact with the surface of the frame, of theback surface of the tape.
 3. The semiconductor wafer assembly of claim1, wherein a cutout corresponding to a cutout showing the crystalorientation of the semiconductor wafer is formed in an outer peripheralportion of the frame and the both cutouts are aligned with each other.4. A semiconductor wafer assembly consisting of an annular frame, a tapemounted to the frame, a semiconductor wafer stuck to the surface of thetape and a fixing ring for fixing the periphery portion of the tape tothe frame, wherein the annular frame consists of an annular frameportion and an annular mounting portion that projects upward from theinner peripheral portion of the frame portion, and the tape is placed tothe surface of the mounting portion and the fixing ring is fitted ontothe outer circumferential portion of the mounting portion to sandwichthe periphery portion of the tape between the outer peripheral surfaceof the mounting portion and the inner peripheral surface of the fixingring.
 5. The semiconductor wafer assembly of claim 4, wherein a cutoutcorresponding to a cutout showing the crystal orientation of thesemiconductor wafer is formed in an outer circumferential portion of theframe and the both cutouts are aligned with each other.
 6. A machiningapparatus comprising chuck tables having a placing surface forsuction-holding a semiconductor wafer assembly and a machining means formachining the semiconductor wafer of the semiconductor wafer assemblysuction-held on each of the chuck tables, wherein the semiconductorwafer assembly consists of an annular frame, a tape mounted to the frameand a semiconductor wafer stuck to the surface of the tape, and each ofthe chuck tables has a semiconductor wafer placing surface forsupporting the back surface of the tape to which the semiconductor waferis stuck and an annular frame placing surface for supporting the backsurface of the frame, formed, in the outer peripheral side of thesemiconductor wafer placing surface, at a position below thesemiconductor wafer placing surface with a level differencetherebetween.
 7. The machining apparatus of claim 6, wherein the leveldifference between the semiconductor wafer placing surface and the frameplacing surface is equivalent to the thickness of the frame.
 8. Themachining apparatus of claim 6, wherein the suction ports ofcommunication paths connected to a suction source are formed in theframe placing surface.
 9. The machining apparatus of claim 6, whereinthe machining means is a grinding means for grinding the semiconductorwafer of the semiconductor wafer assembly.